registry_lookup

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint/idempotent/openWorld/non-destructive, and the description's 'Behavior: read-only' merely repeats that. What it does add beyond annotations is real: 'No key or payment' discloses the auth/cost profile, which matters for deciding whether to call it.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The lead sentence is front-loaded and useful, but the second paragraph largely re-says it ('Use when you want a free lookup of a tool's id and headline score by name, URL fragment or exact endpoint'), and 'Behavior: read-only' duplicates the annotation. Roughly a third of the text does not earn its place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema, the description usefully sketches the return shape (id + headline reliability score). For an optional-parameter, read-only lookup that is largely sufficient, though it never clarifies ordering/pagination implications of `limit` or what happens when no match is found.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 75%, so the schema already documents q, limit and endpoint. The description only restates those keys in prose (and omits `limit` entirely) without adding matching semantics or format constraints beyond what the schema says. Baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (find/lookup) and resource (a tool's id and headline reliability score) plus the three lookup keys. It also names the natural follow-on siblings (registry_tool_badge, registry_tool_detail), so an agent can place it relative to other registry tools without opening a schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives a clear trigger ('check a tool before your agent pays it') and an explicit exclusion ('Not for full detail – use registry_tool_detail'). The one gap is that the adjacent sibling registry_search_tools is never mentioned, leaving the boundary between 'lookup' and 'search' to inference.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.